The device of the present invention pertains to the removal of nails, pins, or dowels from a material, and more particularly pertains to the use of a pneumatic, reverse striking device for pulling nails, pins, or threaded dowels embedding in plastic, concrete, metal, or bones as a result of orthopedic surgery.
The use of fluid actuated or pneumatic actuated devices to extract a workpiece embedded in a material is well known in the prior art. Two examples are the Hartenbach patent, Swiss patent 301,236, and the Schmidt patent, U.S. Pat. No. 3,511,325.
The Hartenbach patent discloses a device which exerts a uniform pulling motion on a pin which is to be removed from a bone. In order to exert the uniform pulling motion on the pin, the device utilized mechanical, hydraulic, pneumatic or electric means to produce rapid striking pulses which cause removal of the pin from the bone. Compressed air is used to drive a cylinder upward to strike a piston, this striking effect as a consequence being transmitted to a pull rod and an intermediate member attached to the bone.
The Schmidt patent discloses a device for extracting sheet piles and jammed drill rods from material. The device includes a tension rod for attachment to the structure to be extracted and a crosshead which is mounted to the top of the tension rod. The device includes a cylinder and within the cylinder is a reciprocable piston. The lower surface of the crosshead has an annular recess which defines a buffer chamber. A buffer liquid, such as hydraulic oil, fills the buffer chamber and absorbs the impact of the piston at the end of the piston's working stroke.
Despite the ingenuity of the above devices, there remains a need for a more efficient and effective device for pulling or extracting nails, pins, and the like from material such as human or animal bone, wood, concrete, or metal.